GAMMA(3M)           UNIX Programmer's Manual            GAMMA(3M)

NAME
     gamma, signgam - log gamma function

SYNOPSIS
     #include <math.h>
     extern int signgam;

     double gamma (x)
     double x;

HP-UX COMPATIBILITY
     Level:    HP-UX/RUN ONLY

     Origin:   System III

DESCRIPTION
     _G_a_m_m_a returns _l_n|G(|_x|)|.  The sign of G(|_x|) is returned in
     the external integer _s_i_g_n_g_a_m.  The following C program frag-
     ment might be used to calculate G:

          y = gamma (x);
          if (y > _l_o_g_m_a_x)
               error ();
          y = exp (y) * signgam;
          /* _l_o_g_m_a_x is floor(ln(maxreal)) */

DIAGNOSTICS
     For negative integer arguments, a huge  value  is  returned,
     and _e_r_r_n_o is set to EDOM.